Thermal processing torches, such as plasma arc torches, are widely used in the heating, cutting, gouging and marking of materials. A plasma arc torch generally includes an electrode, a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap can be used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of an ionized gas with high temperature and sufficient momentum to assist with removal of molten metal.
A problem with existing plasma arc torches, including handheld plasma arc torches, is that they have difficulties flush cutting a workpiece having one or more internal corners due to the axial configuration of the torches. As shown in FIG. 1, a conventional plasma arc torch 100, which includes a rotational symmetric torch tip 102, cannot make a flush cut in the workpiece along the desired path 104. Specifically, the plasma arc torch 100 has difficulty cutting off the protruding flange 106 as close as possible against the horizontal surface 107 of the base 108 without cutting below the horizontal surface 107. Instead, the best cut achievable by the plasma arc torch 100 is indicated by the path 110. As a result, secondary operations, such as grinding, are required to remove the excess workpiece section 112 to achieve the desired flush cut 104. In addition, the closer the plasma arc torch 100 directs a plasma arc flow to the corner of the workpiece, the more likely the arc can inadvertently damage the base 108, such as extending the cut below the horizontal surface 107 of the base 108 along the path 114. Yet another limitation of the plasma arc torch 100 is its inability to ensure that a cut in a workpiece corner is consistently reproducible. For example, the plasma arc torch 100 does not have any positioning mechanism to ensure that the same cut can be made at the same relative location in the corners of different workpieces.